import java.math.BigInteger;
import java.util.StringTokenizer;


class P11448_39643 {

    static String readLn() {
        String newLine = System.getProperty("line.separator");
        StringBuilder buffer = new StringBuilder();
        int car = -1;
        try {
            car = System.in.read();
            while ((car > 0) && (car != newLine.charAt(0))) {
                buffer.append((char) car);
                car = System.in.read();
            }
            if (car == newLine.charAt(0))
                System.in.skip(newLine.length() - 1);
        } catch (java.io.IOException e) {
            return (null);
        }
        if ((car < 0) && (buffer.length() == 0))
            return (null);
        return (buffer.toString()).trim();
    }
   
    public static void main(String[] args) {
        int cases = Integer.parseInt(readLn());
       
        for (int k = 0; k < cases; k++) {
            StringTokenizer st = new StringTokenizer(readLn());
            BigInteger a = new BigInteger(st.nextToken());
            BigInteger b = new BigInteger(st.nextToken());
           
            System.out.println(a.subtract(b));
        }
       
    }
   
}